Indicating cathode-ray tube



1949- H. e. BUSIGNIES 2,459,790

INDICATING CATHODE-RAY TUBE Filed Sept. 5, 1945 A TTOPI EY Patented Jan.25, 1949 UNITED STATES PiATENT- OFFICE r, J V V 1 13 2459390"? 2 Y i itmmoa rnv'c Gammon-RAY TUBE iHenri G..Busignies,:l orest N.. Y., toFederal Telephone and Radio Corporation, .New York, N. Y., a corporationof Delaware Application September 5, 1945, Serial No.',014,5 2f7 Thisinvention relates to cathode ray which are used for indicating purposes.

In certain systems employing cathode ray oscillograph tubes, such as forexample direction finders and radar systems, the time base of the tubeis rotated at a relatively low speed, such as for example, one turn persecond to one turn every three or four seconds. While the direct lightonthe screen of the cathode ray tube as the beam jstrikes the screenis,often observable in'ia fairly brightly illuminated room, the after-glowcannot be seen except in relatively dark rooms. This efiect renders suchindicators unsatisfactory in airplanes and other places whereobservation is made in a fairly brightly illuminated area.

An object of the present invention is the provision of an improvedcathode ray tube for indicating purposes.

Another object of the present invention is the provision of a cathoderay tube in which the indication on the screen persists for a relativelylong time and at a relatively greater intensity, as compared with theindication of the conventional cathode ray tube heretofore employed.

tubes Other and further objects of the present invention will becomeapparent and the invention will be best understood from the followingdescription of an embodiment thereof, reference being had to theaccompanying drawings, in which:

Fig. 1 is a schematic side elevational view of a cathode ray tubeembodying my invention; and

Fig. 2 is a greatly enlarged detailed view of part of the grid of thecathod ray tube of Fig. 1.

Referring now to Fig. 1, the cathode ray tube there illustrated andgenerally designated by the numeral l includes an envelope 2 having theusual type of screen 3 adapted to become illuminated when impinged uponby an electron beam. Tube l includes two electron guns 4 and 5respectively, electron gun 4 emitting a narrow beam as indicated at 6,While electron gun 5 emits a cone-like beam as indicated at 1. Bothelectron guns 4 and 5 are directed at a grid-like electrode 8 interposedbetween said guns and the screen, and which is shown in greater detailin Fig. 2. Electrode or grid 8 is a foraminated structure including aplurality of openings 9 through which electrons may pass. The solid partof the electrode 8 is made up of a large number, such as for example,10,000 to 50,000, tiny particles of conductive material, that is,metallic particles l0 which are insulated from each other, for example,by being embedded as spaced intervals in a nonconductive material ll.

In operation, the beam 6 from electron gun- 4, which ispreferablyof highintensity is rotated or otherwise deflected .by the deflecting meansillustrated schematically and designated by the numeral 12 so that thebeam 6 moves over the surface of electrode. 8 and scans it inapredeterminedinanner. .Atthe'places on the p'erforated electrode -8where the beam-from electron gun E has ahigh intensity, that isat theplaces where 'beam'fi-impinges, theparticles l0 will ac quire a negativecharge. This charge canbe maintained for a given period, of for examplea few seconds or longer and during this period the cone of electrons,that is, beam 1 emitted from electron gun 5 covers the whole area of theelectrode 8. The stream of electrons passing through electrode 8, thatis beam 1, is controlled by the potentials of the particles of theelectrode 8 and therefore the amount of electrons from beam 1 passingthrough electrode 8 will be so controlled as to reproduce on the screen3 an image which will depend upon the charges accumulated on theelectrode 8 due to the action of the electron gun 4. It will thereforebe seen that the image impressed upon the electrode 8 by electron gun 4can be maintained visible on the screen as long as the charges of allthe particles are maintained. The progressive discharge of theseparticles is controlled by suitable choice of the non-conductivematerial II and the attachment of the electrode 8 to the rest of thetube structure, so that the charges dissipate at a predeterminated rate.7

It is preferred to so arrange the electron guns 4 and 5 in relation toscreen 3 that While electron gun 5 is aimed toward the screen, electrongun 4 is so aimed that any of its electrons passing through electrode 8miss the screen. For this purpose the envelope 2 may be bent asindicated at l3 and the guns 4 and 5 arranged in any suitable way, suchas for example as illustrated in Fig. 1; Conventional means may beemployed to collect and return the electrons emitted from the electronguns.

While I have described above the principles of my invention inconnection with specific apparatus, it is to be clearly understood thatthis description is made only by way of example and between said meansand said screen, a plurality of metallic particles disposed, in randomfashion, on said plate on the side thereof facing said means, and meansfor conditioning said electrode so as to p mit the passage of electronsonly through selected ones of the perforations in said plate.

2. A cathode ray: tube comprising means for producing an electron beam,a fluorescent screen arranged in the path of said beam, a perforatedplate of insulating material, saidplatedisposed between said means andsaid screen, a plurality of metallic particles embeddedi 1m said plateon the side thereof facing said meanss-saiil'particles disposed inrandom fashion, and-means for producing an electrostatic charge on themetallicparticles on said plate adjacent selected perforations thereofto control the passage of electrons" through such selected perforations.

3; A cathode ray; tube. according-1th claim 2 wherein said electron:beam covers-substantially theentire surface ofisaid plate.

4. A cathode ray tube according to:- cla'im 2 wherein the means forproducing a charge on said plateinclude means forrproducing a-relativelynarrow electronbeamdirected; toward: said plate,,and means fondefiectingsaidbleanntode termine theareas on said? plate: on which said narrowbeam. impinges,,thereby-- chargingsthe selected areas so as to controlthe flow of electrons through the openings in said selected areas.

5. A cathode ray tube according to claim 2 wherein minute electricallyconductive particles adjacent the selected perforations of said plateare adapted to be electrostatically charged to controfthe fibwfofeleotronsalirongirslected per- 'forationof sail' 'plate rsaid platebeing adapted to dissipate the charge after a given interval.

6. A cathode ray tube according to claim 2 wheneimthe-means forproducing a charge on said plate includes means for producing arelatively namoweiectron beam; directed toward said plate, and meansfor-deflecting said beam to determine the areas" omsaid plate on whichsaid narrow beam-impinges-Tsaidnarrow beam being directed so that theelectrons from said narrow beam passingthrough said plate do not impingeon said screen.

BUSIGNIES;

REFERENCES: CITED The following references are of record in the fi-le ofthis patent Young"- Oct. 21, I941

